Why do some buildings survive earthquakes and others do not?

The photo shows some secondary teachers trying out Earthlearningidea 'Quake shake - will my home collapse?' Their demonstrator is Jothi, from Arul Anandar College, Karumathur, India. You can see at the bottom of the photo that, during an 'earthquake', one 'block of flats' has collapsed and the other has not. Why is that? It is quite important for pupils to know.
As you can see, this activity is easy to set up and is great fun!
If you have any photos of your pupils or teacher trainees carrying out Earthlearningideas, then please send them to us.